Communications in a medical device system with temporal optimization

ABSTRACT

Systems and methods for managing communication strategies between implanted medical devices. Methods include temporal optimization relative to one or more identified conditions in the body. A selected characteristic, such as a signal representative or linked to a biological function, is assessed to determine its likely impact on communication capabilities, and one or more communication strategies may be developed to optimize intra-body communication.

CROSS REFERENCE TO RELATED APPLICATIONS

The present application claims the benefit of and priority to U.S.Provisional Patent Application No. 62/134,752, filed Mar. 18, 2015,titled COMMUNICATIONS IN A MEDICAL DEVICE SYSTEM WITH TEMPORALOPTIMIZATION, the disclosure of which is incorporated herein byreference.

TECHNICAL FIELD

The present disclosure generally relates to medical devices, and moreparticularly to communications between medical devices in a multi-devicesystem.

BACKGROUND

Various active implantable devices are available or in development fortreating and/or diagnosing numerous ailments. Some examples includecardiac assist devices, pacemakers, defibrillators, cardiac monitors,neurostimulation and neuromodulation systems, drug and medication pumps,and others. A patient may have multiple implanted devices and maybenefit in some circumstances by enabling such devices to communicatewith one another. Because these implantable devices are often reliant onbattery power, communication between devices should be designed forefficiency and to limit power consumption.

SUMMARY

The present disclosure relates generally to systems and methods formanaging communication strategies with temporal optimization relative toone or more identified conditions in the body.

A first example is a first medical device comprising: means forcommunicating with a second implantable medical device; means foridentifying a first characteristic having a possible impact oncommunication success; means for selecting a first condition of thefirst characteristic on which to trigger an attempt at communication;means for determining that the first condition of the firstcharacteristic is present and attempting communication with the secondimplantable medical device; means for assessing whether the attemptedcommunication was successful; and means for associating the firstcondition and first characteristic with a reduced likelihood ofcommunication success if the attempted communication was not successful.

A second example takes the form of the first medical device of the firstexample wherein the means for communicating is configured forcommunication by conducted communication. A third example takes the formof a first medical device as in either of the first two examples whereinthe first medical device is configured as an implantable medical device.A fourth example takes the form of a first medical device of any of thefirst three example, further comprising means for associating the firstcondition and first characteristic with an improved likelihood ofcommunication success if the attempted communication was successful.

A fifth example takes the form of a first medical device of any of thefirst four examples further comprising optimization means for selectingmultiple conditions of the first characteristic and repeatedly operatingthe means for determining, means for assessing and means for associatingfor each of multiple conditions of the first characteristic to determinewhether the first characteristic can be used to determine a likelihoodof communication success.

A sixth example takes the form of a first medical device of any of thefirst to fifth examples further comprising means for identifying asecond characteristic, wherein the means for determining, means forassessing and means for assessing are operable to test at least a firstcondition of the second characteristic to determine whether the secondcharacteristic can be used to determine a likelihood of communicationsuccess.

A seventh example takes the form of a first medical device of any of thefirst to sixth examples wherein the first characteristic is a detectedstatus of a cardiac cycle, and the first condition is the occurrence ofone of a cardiac R-wave or a cardiac T-wave. An eighth example takes theform of a first medical device of any of the first to sixth exampleswherein the first characteristic is a detected status of a cardiaccycle, and the first condition is the occurrence of a pacing pulse. Aninth example takes the form of a first medical device of any of thefirst to sixth examples wherein the first characteristic is a detectedstatus of a respiration cycle, and the first condition is the occurrenceof one of an exhale or an inhale. A tenth example takes the form of afirst medical device of any of the first to sixth examples wherein thefirst characteristic is a detected a transthoracic impedance, and thefirst condition is the occurrence of one of a maximum impedance or aminimum impedance. An eleventh example takes the form of a first medicaldevice of any of the first to sixth examples wherein the firstcharacteristic is a cyclic biological phenomenon and the first conditionis the occurrence of a recurring event in the cyclic biologicalphenomenon.

A twelfth example takes the form of an implantable medical device systemcomprising a first medical device as of any of the first to eleventhexamples and a second implantable medical device configured forcommunication with the first medical device, wherein the first medicaldevice is an intracardiac pacing device, and the second implantablemedical device is a subcutaneous defibrillator.

A thirteenth example takes the form of an implantable medical devicesystem comprising a first medical device as in any of the first toeleventh examples, and a second implantable medical device configuredfor communication with the first medical device, wherein the firstmedical device is a subcutaneous defibrillator, and the secondimplantable medical device is an intracardiac pacing device.

A fourteenth example is a first medical device comprising means forcommunicating with a second medical device; means for determining afirst condition of a first characteristic is present; and means formodifying communication with the second implantable medical device basedon the determination; wherein at least one of the first and secondmedical devices is implantable. A fifteenth example takes the form of afirst medical device as in the fourteenth example wherein the firstcharacteristic is a cyclic biological phenomenon and the first conditionis the occurrence of a recurring event in the cyclic biologicalphenomenon.

A sixteenth example is a first medical device comprising a communicationmodule for communicating with a second implantable medical device and acontroller operatively coupled to the communication module for at leastone of receiving or transmitting messages, the controller configured tooptimize communication by: identifying a first characteristic having apossible impact on communication success; selecting a first condition ofthe first characteristic on which to trigger an attempt atcommunication; determining that the first condition of the firstcharacteristic is present and attempting communication with the secondimplantable medical device; assessing whether the attemptedcommunication was successful; and if the attempted communication was notsuccessful, associating the first condition and first characteristicwith a reduced likelihood of communication success.

A seventeenth example takes the form of the first medical device of thesixteenth example wherein the communication module is configured forcommunication by conducted communication. An eighteenth example takesthe form of the first medical device of either the sixteenth orseventeenth examples wherein the first medical device is configured asan implantable medical device. A nineteenth example takes the form ofthe first medical device of any of the sixteenth to eighteenth examples,wherein the controller is further configured to associate the firstcondition and first characteristic with an improved likelihood ofcommunication success if the attempted communication was successful. Atwentieth example takes the form of the first medical device of any ofthe sixteenth to nineteenth examples, wherein the controller isconfigured to further optimize communication by selecting multipleconditions of the first characteristic and repeating the determining andassessing steps for each of multiple conditions of the firstcharacteristic to determine whether the first characteristic can be usedto determine a likelihood of communication success. A twenty-firstexample takes the form of the first medical device of any of thesixteenth to twentieth examples, wherein the controller is configured toidentify a second characteristic and test at least a first condition ofthe second characteristic to determine whether the second characteristiccan be used to determine a likelihood of communication success.

A twenty-second example takes the form of the first medical device ofany of the sixteenth to twenty-first examples wherein the firstcharacteristic is a detected status of a cardiac cycle, and the firstcondition is the occurrence of one of a cardiac R-wave or a cardiacT-wave. A twenty-third example takes the form of the first medicaldevice of any of the sixteenth to twenty-first examples wherein thefirst characteristic is a detected status of a cardiac cycle, and thefirst condition is the occurrence of a pacing pulse. A twenty-fourthexamples takes the form of the first medical device of any of thesixteenth to twenty-first examples wherein the first characteristic is adetected status of a respiration cycle, and the first condition is theoccurrence of one of an exhale or an inhale. A twenty-fifth exampletakes the form of the first medical device of any of the sixteenth totwenty-first examples wherein the first characteristic is a detected atransthoracic impedance, and the first condition is the occurrence ofone of a maximum impedance or a minimum impedance. A twenty-sixthexamples takes the form of the first medical device of any of thesixteenth to twenty-first examples wherein the first characteristic is acyclic biological phenomenon and the first condition is the occurrenceof a recurring event in the cyclic biological phenomenon.

A twenty-seventh example takes the form of an implantable medical devicesystem comprising a first medical device as in any of the sixteenth totwenty-sixth examples and a second implantable medical device configuredfor communication with the first medical device, wherein the firstmedical device is an intracardiac pacing device, and the secondimplantable medical device is a subcutaneous defibrillator. Atwenty-eighth example takes the form of an implantable medical devicesystem comprising a first medical device as in any of the sixteenth totwenty-sixth examples, and a second implantable medical deviceconfigured for communication with the first medical device, wherein thefirst medical device is a subcutaneous defibrillator, and the secondimplantable medical device is an intracardiac pacing device.

A twenty-ninth example is a first medical device comprising acommunication module for communicating with a second medical device anda controller operatively coupled to the communication module messages,the controller configured to optimize communication by: determining afirst condition of a first characteristic is present; and modifyingcommunication with the second implantable medical device based on thedetermination; wherein at least one of the first and second medicaldevices is implantable.

A thirtieth example takes the form of the first medical device of thetwenty-ninth example wherein the first characteristic is a cyclicbiological phenomenon and the first condition is the occurrence of arecurring event in the cyclic biological phenomenon. A thirty-firstexample takes the form of the first medical device of the thirtiethexample wherein the cyclic biological phenomenon is one of a respirationcycle or a cardiac cycle.

A thirty-second example is a method of communication with an implantablemedical device comprising: identifying a characteristic having apossible impact on communication success; selecting a condition of thecharacteristic on which to trigger an attempt at communication;attempting communication based on the condition of the characteristicoccurring; and assessing whether the communication was likelysuccessful.

A thirty-third example takes the form of a method as in thethirty-second example, further comprising: if the communication wassuccessful, associating the characteristic and condition with animproved likelihood of communication success; or if the communicationwas not successful, associating the characteristic and condition with areduced likelihood of communication success.

A thirty-fourth example takes the form of a method as in either of thethirty-second or thirty-third examples wherein the characteristic is acyclic biological phenomenon and the condition is the occurrence of arecurring event in the cyclic biological phenomenon. A thirty-fifthexample takes the form of a method as in the thirty-fourth examplewherein the cyclic biological phenomenon is one of a respiration cycleor a cardiac cycle.

The above summary is not intended to describe each embodiment or everyimplementation of the present disclosure. Advantages and attainments,together with a more complete understanding of the disclosure, willbecome apparent and appreciated by referring to the followingdescription and claims taken in conjunction with the accompanyingdrawings.

BRIEF DESCRIPTION OF THE DRAWINGS

The disclosure may be more completely understood in consideration of thefollowing description of various illustrative embodiments in connectionwith the accompanying drawings, in which:

FIG. 1 illustrates a patient having a plurality of implantable medicaldevices;

FIG. 2 illustrates a block diagram of an implantable medical device;

FIGS. 3-6 are schematic diagrams illustrating communications pulsesrelative to biological signals;

FIGS. 7-11 are flow diagrams of a several illustrative methods that maybe implemented by a medical device or medical device system.

While the disclosure is amenable to various modifications andalternative forms, specifics thereof have been shown by way of examplein the drawings and will be described in detail. It should beunderstood, however, that the intention is not to limit aspects of thedisclosure to the particular illustrative embodiments described. On thecontrary, the intention is to cover all modifications, equivalents, andalternatives falling within the spirit and scope of the disclosure.

DESCRIPTION

The following description should be read with reference to the drawingsin which similar elements in different drawings are numbered the same.The description and the drawings, which are not necessarily to scale,depict illustrative embodiments and are not intended to limit the scopeof the disclosure.

FIG. 1 illustrates a patient having a plurality of implantable medicaldevices. A patient, 10 is shown having a leadless cardiac pacemaker(LCP) 14 implanted inside the heart 12. A subcutaneous implantabledefibrillator (SICD) 16 having a left axillary canister and lead 18extending to electrodes 20 is also shown. The patient may also have aninsulin pump 22, a pain pump 24 for delivering pain medication to theshoulder, and/or a nerve stimulator 26 having a lead (not shown)extending to the neck or head.

Other devices could be substituted for those shown in FIG. 1, and thepositions shown for each device are not intended to be limiting. Someadditional or alternative examples include other pacemakers ordefibrillators such as those with transvenous, intracardiac, epicardial,or substernal leads and/or electrodes, a cardiac monitor, leftventricular assist device, spinal cord stimulator, vagus nervestimulator, gastric electric stimulator, sacral nerve stimulator, and/orany other implantable medical device.

In some embodiments an implanted device may be in communication with oneor more extracorporeal devices. The extracorporeal device(s) may beaffixed to the patient in a wearable configuration. The extracorporealdevice(s) may provide a therapy, for example a nerve stimulationtherapy, muscle simulation therapy and/or respiration therapy (e.g.continuation positive airway pressure therapy). Additionally oralternatively the extracorporeal device may provide a diagnosticfunction, for example a cardiac monitoring function or/and a respiratorymonitoring function. Additionally or alternatively the extracorporealdevice may serve as a communication link between an implanted device anda device not in physical contact with the patient (i.e. remote from thebody). In some embodiments one or more parts/elements of a device orsystem may be implanted and other portions may be extracorporeal (e.g. adrug pump or a continuous glucose monitor).

These various systems may be interrogated by an external device or a“programmer” 28, which may optionally use one or more skin electrodes 30to assist with communication to an implanted device. Skin electrodes 30may be used for conducted communication with an implantable device.Conducted communication is communication via electrical signals whichpropagate via patient tissue and are generated by more or less ordinaryelectrodes. By using the existing electrodes, conducted communicationdoes not rely on an antenna and an oscillator/resonant circuit having atuned center frequency common to both transmitter and receiver.

For other communication approaches such as RF or inductivecommunication, the programmer 28 may instead use a programming wand ormay have an antenna integral with the programmer 28 housing forcommunication. Though not shown in detail, the programmer 28 may includeany suitable user interface, including a screen, buttons, keyboard,touchscreen, speakers, and various other features widely known in theart.

It is unlikely a single patient 10 would have all of the differentsystems implanted as shown in FIG. 1. For purposes of the presentinvention, it is assumed that a patient may have at least twoimplantable systems simultaneously, and it may be beneficial tofacilitate communication between the at least two implantable systems.The mode for communication between two implanted systems may beconducted communication, though other approaches (optical, acoustic,inductive or RF, for example) could be used instead.

FIG. 2 illustrates a block diagram of an implantable medical device. Theillustration indicates various functional blocks within a device 50,including a processing block 52, memory 54, power supply 56,input/output circuitry 58, therapy circuitry 60, and communicationcircuitry 62. The I/O circuitry 58 can be coupled to one or moreelectrodes 64, 66 on the device 50 housing, and may also couple to aheader 68 for attachment to one or more leads 70 having additionalelectrodes 72. The communication circuitry 62 may be coupled to anantenna 74 for radio communication (such as Medradio, ISM, or other RF)and/or may couple via the I/O circuitry 58 to a combination ofelectrodes 64, 66, 72, for conducted communication.

The processing block 52 will generally control operations in the device50 and may include a microprocessor or microcontroller and/or othercircuitry and logic suitable to its purpose. Processing block 52 mayinclude dedicated circuits or logic for device functions such asconverting analog signals to digital data, processing digital signals,detecting events in a biological signal, etc. The memory block mayinclude RAM, ROM, flash and/or other memory circuits for storing deviceparameters, programming code, and data related to the use, status, andhistory of the device 50. The power supply 56 typically includes one toseveral batteries, which may or may not be rechargeable depending on thedevice 50. For rechargeable systems there would additionally be chargingcircuitry for the battery (not shown).

The I/O circuitry 58 may include various switches or multiplexers forselecting inputs and outputs for use. I/O circuitry 58 may also includefiltering circuitry and amplifiers for pre-processing input signals. Insome applications the I/O circuitry will include an H-Bridge tofacilitate high power outputs, though other circuit designs may also beused. Therapy block 60 may include capacitors and charging circuits,modulators, and frequency generators for providing electrical outputs.For devices such as insulin and drug pumps the therapy circuit 60 mayinclude a pump or pump actuator coupled to a delivery system foroutputting therapeutic material, rather than using the I/O circuitry 58as would be typical for systems that generate an electrical therapyoutput.

Communications circuitry 62 may include a frequency generator/oscillatorand mixer for creating output signals to transmit via the antenna 74.Some devices 50 may include a separate ASIC for the communicationscircuitry 62, for example. For devices using an inductive communicationoutput, an inductive coil may be included. Devices may also use opticalor acoustic communication approaches, and suitable circuits,transducers, generators and receivers may be included for these modes ofcommunication as well or instead of those discussed above.

As those skilled in the art will understand, additional circuits may beprovided beyond those shown in FIG. 2. For example, some devices 50 mayinclude a Reed switch or other magnetically reactive element tofacilitate magnet wakeup or reset of the device by a user. Some systemsmay omit one or more blocks, for example, an implantable cardiac monitorcan omit therapy block 60, and an LCP may exclude the header 68 forcoupling to lead 70.

In several embodiments, the present invention is directed toward themanagement and optimization of conducted communication between twoimplanted medical devices. For example, an LCP may communicate with anSICD. The LCP may, for example, provide a detected heartbeat rate to theSICD in order to assist the SICD in making a therapy determination. Inanother example, the SICD may request status from the LCP or may directthe LCP to deliver pacing pulses.

Other combinations of systems may use conducted communication betweendevices for various reasons. For example, if a patient has both a drugpump and a spinal cord stimulator, the drug pump may communicate to thespinal cord stimulator that it is in need of servicing, such that bothsystems may use their internal annunciating mechanisms to alert thepatient that the drug pump requires service. As integrated systemsdevelop, it may become possible to develop simplified devices that omit,for example, standard telemetry or annunciator circuits, and instead useconducted communication to another device that includes full telemetryand annunciator circuits. If telemetry and/or annunciator circuits areomitted in one or more devices, the devices may become smaller and powerconsumption may be reduced. Thus conducted communication optimizationmay facilitate development of smaller and/or longer lasting devices inaddition to facilitating inter-device coordination for therapy purposes.

FIGS. 3-6 are schematic diagrams illustrating communications packetsrelative to biological signals. Conducted communication taking placewithin the body is subject to interference from various biologicalfunctions. Respiration and the cardiac cycle are two particular cyclicbiological functions of interest, though any other biological function,cyclic or not, may also be addressed using the methods and devicesherein.

FIG. 3 illustrates an ECG signal at 100, and communications by Device Aat 102 and Device B at 104. The ECG shows a QRS complex (a heartbeat) at106 followed by an interval 108, and another beat at 110. In thisillustration, Device A sends a data packet 112 during the interval 108between beats 106, 110, and Device B responds with a packet at 114during the same interval 108. In another embodiment, Device B mayrespond after the subsequent beat at 110.

The phrase “data packet” is used for convenience and should beunderstood as generically including any type of message sent from onedevice to another. No particular message/frame structure, type of data,size or other meaning should be implied.

In FIG. 3, the data packets are shown as being sent independent oftherapy output by either Device A or Device B. FIG. 4 shows a scheme inwhich Device B is configured to embed communications in a therapyoutput. The ECG is shown at 120, and the therapy output of Device B isshown at 124, while the communications from Device A are shown at 126.The therapy output 124 includes pacing pulses 130 and 136, which triggerbeats 132 and 138 respectively on the ECG 120.

A detail view of pacing pulse 130 is shown below, and it is seen at 142that the shape of the pacing pulse 130 includes amplitude modulationembedding a data packet. Other approaches to embedding information in apacing pulse can be used; the illustration is simplified in FIG. 4 sincethe present invention is not limited to embedding data in a therapyoutput nor is it limited to communicating via therapy output-encodeddata. Preferably, the embedded data 142 does not affect theeffectiveness of therapy of the pacing pulse 130.

Device A is designed to recognize the data 142 embedded in the pacingpulse 130. In this example, Device A responds with a data packet aftersome delay such that data packet 134 follows the end of the QRS complexof beat 132. In an alternative, Device A could sent data packet 134 andDevice B would respond with a message embedded in pacing pulse 136.

The signals for conducted communication are generally intended to haveamplitudes that will not cause cardiac or skeletal muscle contraction,with the exception of the case in which the conducted communication isembedded in a stimulus signal, such as pacing pulse 130 with data 132.The patient should not be aware of the conducted communication signal.

In FIG. 4, the amplitude, duration and/or frequency content of the datapacket 134 would be selected to avoid stimulating muscle (skeletal orcardiac). Delivery of the data packet 134 during the QRS complex 132could cause Device B to miss the signal or interpret it as part of theQRS complex 132. Therefore, as indicated at 140, the data packet 134 ispreferably delivered after the conclusion of the QRS complex for beat132, and preferably ends before delivery of the next pacing pulse 136.

One approach to delivering data packet 134 would be to call for a fixeddelay after the conclusion of the pacing pulse 130, such as a 300millisecond delay allowing for the (typically wide) paced QRS complexfor beat 132 to be finished. Another approach would be to sense the ECG120 for termination of the QRS. Each approach has limitations, however.A fixed period may not account for other portions of the ECG, such asthe T-wave and/or S-T segment, which can vary in amplitude betweenpatients and even within a patient based on the patient's posture,activity level, etc. Detecting the end of the QRS can be highlydependent on the location of the electrodes used to sense the ECG 120.Moreover, it may be more effective if both Device A and Device B knowwhen the data packet 134 is expected. Thus a temporal optimization maybe highly useful to enhance communication reliability.

As used in the present disclosure, the ECG represents the electricalstate of the patient's heart, and is a “characteristic” of the patient.The occurrence of a QRS complex, or other event, in the ECG represents a“condition” of the ECG characteristic. Other characteristics andconditions of characteristics are discussed below.

FIG. 5 illustrates another characteristic and an illustrative example ofits use. Here, a transthoracic impedance is shown at 160, an ECG isshown at 162, and the communication packets for Device A and Device Bare shown at 164 and 166, respectively. The transthoracic impedance 160may vary with patient movement, such as respiration. In this sequence,the beats of the ECG are avoided by Device A when it sends out datapackets 170 and 180. However, Device B fails to respond at 172 to datapacket 170. Reviewing the transthoracic impedance suggests that a hightransthoracic impedance at 174 may have negatively affectedcommunication of data packet 170. This may be treated as a “highcondition” of the “characteristic” of transthoracic impedance.

As a result, in this embodiment, the method includes delivering the nextpacket 180, both outside of the QRS complex of ECG 162, but also at apoint where the transthoracic impedance 160 is low as shown at 184. Thistime, the data packet 180 is received by device B, generating anacknowledgement or other responsive output at 182. Analysis of theobserved characteristic (impedance), suggests that the condition of lowtransthoracic impedance at 184 may have positively impacted the successof data packet 180. The illustrative system may record one or both ofthe success and failure as indicating a likely connection betweentransthoracic impedance and communication success. Reviewing FIG. 5alongside FIG. 4 shows that a temporal optimization may take intoaccount multiple characteristics.

The QRS complex is not the only condition which may arise within the ECGcharacteristic; the T-wave and P-wave, for example, or S-T segmentelevation, are also potential conditions that may impact communicationsuccess. In FIG. 6, the ECG is represented at 200, and communicationsactivity of Devices A and B is shown at 202 and 204 respectively.

Device A attempts communication at 210, but the communication fails tobe observed by Device B, which does not reply at 212 as expected. Closerreview of the ECG 200 indicates that the QRS complex is followed by aprominent T-wave shown at 214. Either of Device A or Device B may assessthe ECG and the failed communication attempt and identify a likelyrelationship, and make an adjustment to the timing of a latercommunication attempt.

In an alternative example, Device A may not identify whether there is aprominent T-wave; it simply knows that the communication attempt at 210was not acknowledged. Therefore Device A can adjust the delay after theR-wave detection, shown at 216, by increasing or decreasing the delay.Here, Device A adjusts such that the next attempt in which data packet220 is sent occurs with a greater delay 226. This time, the T-wave 224is missed, and the data packet 220 is received and acknowledged byDevice B at 222. As illustrated by FIGS. 4-6, not only are theremultiple characteristics to be potentially aware of, but also multipleconditions within the characteristics.

For purposes herein, the ECG, transthoracic impedance, and status of therespiration cycle are three possible characteristics. Anothercharacteristic may include posture, which may be determined by use of anaccelerometer or through analysis of some other signal such as skeletalmuscle activity, the shape or amplitude of a respiration signal, or ECGmorphology from one or more sensing vectors. If the patient isexercising, there may be a detectable cycle associated with motionartifacts generated with the patient's stride. For example, at eachfoot-strike if the patient is running, a monitored biological electricalsignal or a monitored accelerometer output, for example, may demonstratea motion artifact. Testing communication success relative to thedetected motion artifact may be useful in determining whether and howcommunication success can be ensured when the artifact is identified. Insome examples, the QRS and cardiac signal may actually not be ofsignificant importance to communication success, and other factors maybe deemed more likely to create marginal or poor communication, such asthose non-ECG items just noted.

It should be noted in this context that an implantable medical devicecommunication system may have multiple reasons for communicating. Somecommunication is not urgent, as for example, a periodic device statuscheck communication. Other communication is urgent, as for example, arequest that a device deliver therapy or prepare to have therapydelivered by a second device. A specific example would be thecombination of an LCP and SICD, where the SICD may non-urgently requestbattery status from the LCP periodically (i.e. weekly), and may onoccasion urgently request that the LCP provide a beat rate measurementconfirmation prior to the SICD delivering a high power defibrillationshock to the patient, where the LCP rate measurement confirmation wouldbe used to prevent inappropriate shocks due to malsensing.

For another example, an SICD used in combination with a spinal cordstimulator (SCS) may use an urgent communication to allow the SICD towarn the SCS that a high energy defibrillation shock, which couldoverwhelm the SCS sensing circuitry inputs, is about to be delivered sothat the SCS can suspend sensing or isolate its sensing circuitry duringthe shock. Temporal optimization may be performed using the non-urgentcommunication requests, to give greater confidence that an urgentrequest will be received successfully.

FIGS. 7-11 are flow diagrams of a several illustrative methods that maybe implemented by a medical device or medical device system. Startingwith FIG. 7, the illustrative method begins with identifying acharacteristic at 250, then selecting a condition at 252 to assess forits potential impact on communication. Next, the condition andcharacteristic are monitored and an attempt at communication is made, asshown at 254. The communication effort is then assessed at 256. Theassessment at 256 may be a simple pass/fail assessment, or may include amore complex analysis such as review of the signal-to-noise ratio,signal strength, frame or bit error rate, presence or lack ofacknowledgement/handshake, presence or lack of an intended response(therapy or other), measurement of link availability or speed, or otherfeature of the communication attempt, for example as discussed incommonly assigned U.S. Provisional Patent Application 62/134,726, filedMar. 18, 2015 and titled COMMUNICATIONS IN A MEDICAL DEVICE SYSTEM WITHLINK QUALITY ASSESSMENT the disclosure of which is incorporated hereinby reference.

While several examples rely on electrical signals (myopotential orneuropotential, for example) and potential interference with conductedcommunication, other combinations are possible. For example, an acousticcommunication system may consider heart sounds or respiratory sounds,rather than myopotentials.

Using the assessment at 256, an association can be generated at 258.Steps 252, 254 and 256 may be repeated for other conditions, asindicated at 260, of the same characteristic. In an additional loopindicated at 262, other characteristics may also be assessed. Ifdesired, further combinations of characteristics and conditions may beconcatenated for testing as well. Optionally, a probability map may begenerated, as indicated at 264. Such a map may include possiblecommunication pathways (such as links and configurations of devices) andsets of probabilities of success given particular parameters, forexample. A probability map may be used by an individual device or systemto plot out communication strategies, or it may be exported fordiagnostic and system design purposes. In addition, as indicated at 266,settings for the system under test may also be generated, including, forexample, if-then type rules for planning communication timing relativeto identified conditions and characteristics.

For example, the ECG may be identified as a characteristic at 250, and acondition in which the ECG is above a threshold amplitude may beidentified, with testing performed at 254 by attempting to communicate adata packet with the ECG at certain amplitude levels, using a loopingapproach indicated by block 260. Attempts may be made, for example, withthe ECG showing an R-wave as one condition, a T-wave as anothercondition, and being near baseline during the interval between a T-waveand a subsequent P-wave as yet another condition. The attempts areassessed at 256, and an association is constructed at 258. A probabilitymap can be generated at 264. The system can be appropriately set at 266to provide temporal optimization such that communication attempts occurat times within the ECG cycle selected to maximize the chance ofsuccess. As part of the setting step at 266, or the mapping at 264, datamay be communicated to other implanted devices regarding the settings tobe applied.

If desired and available, variations on the communication signal mayalso be applied, for example, if variable output signal amplitude ordata rate are available, different communication variations may also beapplied to assess their effect on communication success. For example, asystem may determine whether reducing the data rate or increasing signalamplitude can affect the likelihood of communication success. The samecharacteristic and condition can be repeatedly tested with differentconfigurations of the communication signal.

The illustration of FIG. 7 takes a prospective, forward looking approachin which communication ability is assessed under selected conditions.FIG. 8 shows an alternative approach in which, given a particularcommunication attempt, a backward looking review can be undertaken totroubleshoot failures. In FIG. 8, communication is attempted by sendinga data packet from one device to another, as shown at 270. The success,or failure, of the attempt is observed at 272, and then a physiologicalcharacteristic and its condition at the time of the communicationattempt is observed as noted at 274. A correlation is determined, asshown at 276, and subsequent communication can be planned accordinglyby, for example, increasing or reducing a delay relative to anobservable phenomenon. The correlation stored at 276 can be tested andretested over time to determine whether it accurately reflects realworld conditions.

As an example, with a patient who exercises, there may be a cyclicmotion artifact in a detected biological signal associated with thepatient's stride, or swim stroke, or other repetitive motion. An attemptat communication is made at 270 and fails at 272. It is then determinedat 274 how the failed communication attempt related, in time, to themotion artifact. The motion artifact may be determined by sensing thecommunication channel or by observing a separately sensed channel. Acorrelation is presumed at 276 and stored for later reference, and plansare made at 278 to ensure that a subsequent attempt at communicationwill occur with a different temporal relationship to the motion artifact(if such an artifact is observed). The plan at 278 may then becommunicated throughout the system, if desired.

FIG. 9 provides another example. A communication metric, such asamplitude or signal-to-noise ratio, is measured for a given data packetor communication attempt at 300. A potentially related physiologicalcondition is also observed, as shown at 302. A probability of successgiven the communication metric is generated at 304. The communicationstrategy is then configured at 306, using the condition of thephysiological characteristic observed at 302.

As an example, the respiratory cycle of a patient may be observed bytracking transthoracic impedance over time. A communication attempt maybe made and characteristics observed in relation to the communicationattempt would be measured in block 300. The status of the respirationcycle is observed using block 302, and mapping of the probability ofcommunication success based on the point in the respiration cycle atwhich communication is attempted can be generated at 304. Thencommunication attempts for future use can be configured in block 306.

If, for example, the phase of respiration at which the transthoracicimpedance is at a minimum shows better communication metrics than thepoint of maximum transthoracic impedance, then the map of probability at304 would be used to configure communications to occur while minimumtransthoracic impedance is occurring. On the other hand, the probabilitymapping at 304 may determine from the observed communication metricsthat the respiration cycle is not likely to impact communication successor failure. If that is the case, then a different characteristic andcondition may instead be assessed, and the system would record dataindicating that a configuration based on respiration cycle may not behelpful.

FIG. 10 shows another example. A physiological cycle is identified at360. Communication is attempted and fails at 362. (Steps 360 and 362 maybe reversed with the physiological cycle identified in response to orafter failure). A delay relative to an event within the observed cycleis then configured at 364, and a retry scheduled at 366. If the retryfails, the method returns to 364 and configures a different delayrelative to the cycle. Multiple retries may be attempted. A retry limitmay be enforced, for example, with no more than 3-10 retries (or more orfewer, as desired). Eventually the system either retries to success at368, or reaches a timeout 370 in which case an alert may be set relativeto communication difficulty.

FIG. 11 shows another example in which different treatment is given tocritical and non-critical issues. Here, beginning with a need forcommunication at 400, an attempt is made at 402 and fails. It is thendetermined whether a critical or urgent issue has arisen at 404. Forsome urgent issues, the method may execute one or more retries at 406and then proceed regardless of success, or the retry may be bypassedentirely as indicated by the dashed line.

For example, if an SICD is attempting to cause an LCP to deliverantitachycardia pacing (ATP) because the SICD is about to prepare fordefibrillation therapy, no retries may be called if the retry interruptstherapy preparation, as the patient may be suffering a life-threateningsituation. On the other hand, if the SICD can attempt to call for ATPwithout interrupting therapy preparations (which may take severalseconds as capacitors are charged to therapy levels), one or severalretries 406 may be attempted during therapy preparation.

If a non-critical issue is occurring at 404, then an adjustment is madefor a physiological condition at 410 and a number of retries may beattempted in a loop between 410 and 412. Upon success, the parameters414 of a successful communication attempt would be stored for later use.If the number of retries is limited at 412 and the maximum retry limitis reached, then the system may set an error flag or annunciate an errorcondition 416.

A first non-limiting example takes the form of a first medical devicecomprising: means for communicating with a second implantable medicaldevice; means for identifying a first characteristic having a possibleimpact on communication success; means for selecting a first conditionof the first characteristic on which to trigger an attempt atcommunication; means for determining that the first condition of thefirst characteristic is present and attempting communication with thesecond implantable medical device; means for assessing whether theattempted communication was successful; and means for associating thefirst condition and first characteristic with a reduced likelihood ofcommunication success if the attempted communication was not successful.

In this first non-limiting example, the means for communicating may takethe form of, for example, the communication subsystem 62 in FIG. 2,optionally including the antenna 74 or, alternatively, for a conductedcommunication system, the I/O subsystem 58 of FIG. 2 and one or more ofelectrodes 64, 66 or 72. The means for identifying a firstcharacteristic condition may include an instruction set or sets forperforming a step or steps as described in association with block 250 ofFIG. 7, which may be stored in memory 54 of FIG. 2 or which can beperformed by a processing circuitry 52, or such means may includededicated circuitry, for example, of the processing circuitry 52.

Further in the first non-limiting example, the means for selecting afirst condition of the first characteristic on which to trigger anattempt at communication may include an instruction set stored in memory54 for operation by processing circuitry 52 of FIG. 2, instructionsembedded in processing circuitry 52 of FIG. 2, or dedicated circuitry ofthe processing circuitry 52 of FIG. 2, which are configured to perform astep as described in association with block 252 of FIG. 7. Also in thefirst non-limiting example, the means for determining that the firstcondition of the first characteristic is present and attemptingcommunication with the second implantable medical device may include aninstruction set stored in memory 54 for operation by processingcircuitry 52 of FIG. 2, instructions embedded in processing circuitry 52of FIG. 2, or dedicated circuitry of the processing circuitry 52 of FIG.2, which are configured to perform a step as described in associationwith block 255 of FIG. 7, in which the processing circuitry is furtherconfigured to direct and/or make use of the communications circuitry 62and antenna 74 and/or the I/O circuitry 58 and one or more of electrodes64, 66 or 72.

In the first non-limiting example, the noted means for assessing whetherthe attempted communication was successful may include an instructionset stored in memory 54 for operation by processing circuitry 52 of FIG.2, instructions embedded in processing circuitry 52 of FIG. 2, ordedicated circuitry of the processing circuitry 52 of FIG. 2, which areconfigured to perform a step as described in association with block 256of FIG. 7. Finally in the first non-limiting example, the means forassociating the first condition and first characteristic with a reducedlikelihood of communication success if the attempted communication wasnot successful may include an instruction set stored in memory 54 foroperation by processing circuitry 52 of FIG. 2, instructions embedded inprocessing circuitry 52 of FIG. 2, or dedicated circuitry of theprocessing circuitry 52 of FIG. 2, which are configured to perform astep as described in association with block 258 of FIG. 7, which isconfigured for operation in the event the attempted communication is notsuccessful.

An extension of this first non-limiting example may further comprise ameans for associating the first condition and first characteristic withan improved likelihood of communication success if the attemptedcommunication was successful, which may include an instruction setstored in memory 54 for operation by processing circuitry 52 of FIG. 2,instructions embedded in processing circuitry 52 of FIG. 2, or dedicatedcircuitry of the processing circuitry 52 of FIG. 2, which are configuredto perform a step as described in association with block 258 of FIG. 7,which is configured for operation in the event the attemptedcommunication is not successful.

Another extension of this first non-limiting example further comprisesoptimization means for selecting multiple conditions of the firstcharacteristic and repeatedly operating the means for determining, meansfor assessing and means for associating for each of multiple conditionsof the first characteristic to determine whether the firstcharacteristic can be used to determine a likelihood of communicationsuccess, wherein the optimization means may include an instruction setstored in memory 54 for operation by processing circuitry 52 of FIG. 2,instructions embedded in processing circuitry 52 of FIG. 2, or dedicatedcircuitry of the processing circuitry 52 of FIG. 2, which are configuredto perform a step as described in association with block 260 of FIG. 7.

Still another extension of this first non-limiting example furthercomprises a means for identifying a second characteristic, wherein themeans for determining, means for assessing and means for assessing areoperable to test at least a first condition of the second characteristicto determine whether the second characteristic can be used to determinea likelihood of communication success, wherein the means for identifyinga second characteristic may include an instruction set stored in memory54 for operation by processing circuitry 52 of FIG. 2, instructionsembedded in processing circuitry 52 of FIG. 2, or dedicated circuitry ofthe processing circuitry 52 of FIG. 2, which are configured to perform astep as described in association with block 262 of FIG. 7.

A second non-limiting example takes the form of a first medical devicecomprising means for communicating with a second medical device; meansfor determining a first condition of a first characteristic is present;and means for modifying communication with the second implantablemedical device based on the determination; wherein at least one of thefirst and second medical devices is implantable.

In this second non-limiting example, the means for communicating maytake the form of, for example, the communication subsystem 62 in FIG. 2,optionally including the antenna 74 or, alternatively, for a conductedcommunication system, the I/O subsystem 58 of FIG. 2 and one or more ofelectrodes 64, 66 or 72.

Also in this second non-limiting example, the means for determining afirst condition of a first characteristic is present may include aninstruction set stored in memory 54 for operation by processingcircuitry 52 of FIG. 2, instructions embedded in processing circuitry 52of FIG. 2, or dedicated circuitry of the processing circuitry 52 of FIG.2, which are configured to obtain information regarding one or more ofthe state of the patient's ECG, the patient's measurable impedance, abiological cycle, or other measurable element such as the output of anaccelerometer to determine a condition of a first characteristic.

Finally in the second non-limiting example, the means for modifying mayinclude an instruction set stored in memory 54 for operation byprocessing circuitry 52 of FIG. 2, instructions embedded in processingcircuitry 52 of FIG. 2, or dedicated circuitry of the processingcircuitry 52 of FIG. 2, which are configured to adjust one or moreparameters of a communication subsystem 62 in FIG. 2, optionallyincluding the antenna 74 or, alternatively, for a conductedcommunication system, the I/O subsystem of FIG. 2.

Those skilled in the art will recognize that the present disclosure maybe manifested in a variety of forms other than the specific examplesdescribed and contemplated herein. For instance, as described herein,various examples include one or more modules described as performingvarious functions. However, other examples may include additionalmodules that split the described functions up over more modules thanthat described herein. Additionally, other examples may consolidate thedescribed functions into fewer modules. Accordingly, departure in formand detail may be made without departing from the scope and spirit ofthe present disclosure as described in the appended claims.

What is claimed is:
 1. A first medical device comprising a communicationmodule for communicating with a second implantable medical device and acontroller operatively coupled to the communication module for at leastone of receiving or transmitting messages, the controller configured tooptimize communication by: identifying a first characteristic having apossible impact on communication success; selecting a first condition ofthe first characteristic on which to trigger an attempt atcommunication; determining that the first condition of the firstcharacteristic is present and attempting communication with the secondimplantable medical device; assessing whether the attemptedcommunication was successful; and if the attempted communication was notsuccessful, associating the first condition and first characteristicwith a reduced likelihood of communication success.
 2. The first medicaldevice of claim 1 wherein the communication module is configured forcommunication by conducted communication.
 3. The first medical device ofclaim 1 wherein the first medical device is configured as an implantablemedical device.
 4. The first medical device of claim 1, wherein thecontroller is further configured to associate the first condition andfirst characteristic with an improved likelihood of communicationsuccess if the attempted communication was successful.
 5. The firstmedical device of claim 1, wherein the controller is configured tofurther optimize communication by selecting multiple conditions of thefirst characteristic and repeating the determining and assessing stepsfor each of multiple conditions of the first characteristic to determinewhether the first characteristic can be used to determine a likelihoodof communication success.
 6. The first medical device of claim 1,wherein the controller is configured to identify a second characteristicand test at least a first condition of the second characteristic todetermine whether the second characteristic can be used to determine alikelihood of communication success.
 7. The first medical device ofclaim 1, wherein the first characteristic is a detected status of acardiac cycle, and the first condition is the occurrence of one of acardiac R-wave or a cardiac T-wave.
 8. The first medical device of claim1, wherein the first characteristic is a detected status of a cardiaccycle, and the first condition is the occurrence of a pacing pulse. 9.The first medical device of claim 1, wherein the first characteristic isa detected status of a respiration cycle, and the first condition is theoccurrence of one of an exhale or an inhale.
 10. The first medicaldevice of claim 1, wherein the first characteristic is a detected atransthoracic impedance, and the first condition is the occurrence ofone of a maximum impedance or a minimum impedance.
 11. The first medicaldevice of claim 1, wherein the first characteristic is a cyclicbiological phenomenon and the first condition is the occurrence of arecurring event in the cyclic biological phenomenon.
 12. An implantablemedical device system comprising a first medical device as recited inclaim 1 and a second implantable medical device configured forcommunication with the first medical device, wherein the first medicaldevice is an intracardiac pacing device, and the second implantablemedical device is a subcutaneous defibrillator.
 13. An implantablemedical device system comprising a first medical device as recited inclaim 1, and a second implantable medical device configured forcommunication with the first medical device, wherein the first medicaldevice is a subcutaneous defibrillator, and the second implantablemedical device is an intracardiac pacing device.
 14. A first medicaldevice comprising a communication module for communicating with a secondmedical device and a controller operatively coupled to the communicationmodule messages, the controller configured to optimize communication by:determining a first condition of a first characteristic is present; andmodifying communication with the second implantable medical device basedon the determination; wherein at least one of the first and secondmedical devices is implantable.
 15. The first medical device of claim14, wherein the first characteristic is a cyclic biological phenomenonand the first condition is the occurrence of a recurring event in thecyclic biological phenomenon.
 16. The first medical device of claim 15,wherein the cyclic biological phenomenon is one of a respiration cycleor a cardiac cycle.
 17. A method of communication with an implantablemedical device comprising: identifying a characteristic having apossible impact on communication success; selecting a condition of thecharacteristic on which to trigger an attempt at communication;attempting communication based on the condition of the characteristicoccurring; assessing whether the communication was likely successfuland: if the communication was successful, associating the characteristicand condition with an improved likelihood of communication success; orif the communication was not successful, associating the characteristicand condition with a reduced likelihood of communication success; andconfiguring the implantable medical device to monitor the characteristicfor occurrence of the condition and avoid communication in responsethereto if the characteristic and condition are associated with areduced likelihood of communication success.
 18. The method of claim 17further comprising configuring the implantable medical device to monitorthe characteristic for occurrence of the condition and communicate inresponse thereto if the characteristic and condition are associated withan improved likelihood of communication success.
 19. The method of claim17 wherein the characteristic is a cyclic biological phenomenon and thecondition is the occurrence of a recurring event in the cyclicbiological phenomenon.
 20. The method of claim 19 wherein the cyclicbiological phenomenon is one of a respiration cycle or a cardiac cycle.